Diffusion of light in the atmosphere primarily takes place due to dust particles and other suspended particles, as well as water vapors.

1. Dust particles: Particles of dust, pollutants, and other suspended solid matter in the atmosphere can scatter light as it passes through. These particles are of various sizes and compositions, and when sunlight or other sources of light interact with them, they cause the light to scatter in different directions. This scattering of light by dust particles is responsible for phenomena such as Rayleigh scattering, which gives rise to the blue color of the sky.

2. Water vapors: Water vapor, which is in the form of gaseous water in the atmosphere, can also scatter light. The presence of water vapor in the air can lead to the scattering of light rays, contributing to the diffusion of light. This scattering is particularly evident in the form of clouds, fog, and mist, where the water droplets or ice crystals in the air cause the light to scatter and create a diffused appearance.

3. Carbon dioxide and helium: While carbon dioxide and helium are present in the Earth`s atmosphere, they do not significantly contribute to the diffusion of light. Carbon dioxide primarily absorbs and emits infrared radiation, contributing to the greenhouse effect, while helium, being a noble gas, is chemically inert and does not interact strongly with light.

Therefore, the correct options for the diffusion of light in the atmosphere are dust particles and water vapors.